Substantial progress has been made in the development of re-keyable cylinder and plug assemblies for cabinet locks, such as the technique described in my issued U.S. Pat. No. 4,920,774 titled SELF ALIGNING RE-KEYABLE PIN TUMBLER CABINET DOOR LOCK and my issued U.S. Pat. No. 4,899,563 titled RE-KEYABLE PIN TUMBLER DRAWER LOCK AND PIN TUMBLER CABINET DRAWER LOCK. In my previous '774 patent, the cylinder and plug assembly is forwardly removable merely by releasing a set screw with a conventional screwdriver. The cylinder and plug assembly may then be readily disassembled for replacement of the pins to re-key the lock. Upon reinsertion of the cylinder and plug assembly into the lock body, a guide mechanism insures that a threaded bore in the cylinder and plug assembly aligns with an aperture in the unitary lock shell so that the screw may be quickly reengaged. Prior to my self aligning, re-keyable pin tumbler cabinet door lock described in my U.S. Pat. No. 4,920,744 and my re-keyable cabinet and door lock described in my parent U.S. Pat. No. 4,899,563, the disclosures of which are incorporated herein by reference, cabinet and drawer locks employing releasable cylinder and plug assemblies generally required the use of special tools or complex assemblies which render re-keying of locks of this type economically unfeasible.
Although my above identified locks have been commercialized and have achieved substantial commercial success, the use of a screwdriver is nevertheless required to release the cylinder and plug assembly from the lock's unitary shell. Although screwdrivers are readily available, picking up a tool, using the tool and placing the tool down requires time which could otherwise be applied towards disassembly of the removed cylinder and plug assembly and towards replacement of the tumbler pins.
The theoretical application of a push button release to a cylinder and plug assembly would significantly reduce the time required to remove and reinsert a cylinder and plug assembly into my unitary shell lock body. In addition, a non-removable release button would avoid the possibility of losing the set screw on my above described locks.
The fundamental concept of applying a spring loaded release mechanism to a cylinder and plug assembly is well known. Devices of this type are disclosed in U.S. Pat. No. 1,914,639 to Hurd, U.S. Pat. Nos. 2,058,895 and 2,039,244 to Lowe and U.S. Pat. No. 3,527,071 to Warnod. In each of these devices however, complex machining steps and construction techniques are involved in production of the release mechanism. The expense involved in such machining and construction is generally unacceptable for cabinet door and drawer locks (which are relatively inexpensive applications). Hurd, for example employs has a non-springloaded, release button which reciprocates in a bore. The open end of the bore must be peened from the inside to prevent the release button from escaping from the bore. Such interior peening is relatively expensive and thus counterproductive to the development of an economical, re-keyable cabinet door or drawer lock. The mortice type lock shown in the Hurd '639 patent is a relatively expensive type of lock which can justify an expensive peening step.
The release buttons disclosed in the Lowe '895 patent require expensive milling steps to develop squared off bores in which springloaded release buttons having squared off sides reciprocate. The Lowe '895 device is intended for use in automobiles which justifies the relatively high manufacturing cost of providing squared off bores. Furthermore, other springloaded lock release devices such as those disclosed in U.S. Pat. No. 3,919,867 to Lipschutz et al., U.S. Pat. No. 337,093 to Thistle, and U.S. Pat. No. 2,039,244 to Lowe require the use of special tools to depress the release button. The use of special tools to effect re-keying renders universal re-keyability by locksmiths impractical.
Therefore a need exists for a re-keyable cabinet and drawer lock having a removable cylinder and plug assembly which can be released by a relatively inexpensive push button mechanism.